The present invention relates to capacity modulation of compressors. More particularly, the present relates to the capacity modulation of a scroll compressor by controlling the fluid pressure in a chamber where the fluid pressure in the chamber biases the two scrolls together.
Capacity modulation is often a desirable feature to incorporate into the compressors of air conditioning and refrigeration systems in order to better accommodate the wide range of loading to which the systems may be subjected. Many different approaches have been utilized for providing this capacity modulation feature. These approaches have ranged from control of the suction inlet of the compressor to bypassing compressed discharge gas back into the suction pressure zone of the compressor. With a scroll-type compressor, capacity modulation has often been accomplished by using a delayed suction approach which comprises providing ports at various positions along the scroll wrap which, when opened, allow the initially formed compression chambers between the intermeshing scroll wraps to communicate with the suction zone of the compressor, thereby delaying the point at which the sealed compression chambers are formed and, thus, delaying the start of compression of the suction gas. This method of capacity modulation has the effect of actually reducing the compression ratio of the compressor. While these delayed suction systems are effective at reducing the capacity of the compressor, they are only able to provide a predetermined amount of compressor unloading with the amount being determined by the position of the unloading ports along the scroll wraps. While it is possible to provide multiple step unloading by incorporating a plurality of unloading ports at different locations, this approach becomes costly and it requires additional space to accommodate the separate controls for opening and closing each set of ports. Even when using multiple unloading ports, it is typically not possible to control the capacity of the compressor between 0% and 100% using this delayed suction technique.
More recently, compressor unloading and, thus, capacity modulation has been accomplished by cyclically effecting axial or radial separation of the two scroll members for predetermined periods of time during the operating cycle of the compressor. In order to facilitate the axial unloading or axial separation of the two scroll members, a biasing chamber is formed in or adjacent one of the two scroll members; and this biasing chamber is placed in communication with a source of compressed fluid in a pressure chamber or the discharge chamber of the compressor. The fluid in the biasing chamber is cyclically released to the suction area of the compressor to facilitate the unloading of the compressor.
While the prior art devices have performed satisfactorily in the field, their designs have required the addition of the specific biasing chamber, as well as the control systems needed to control the flow of the pressurized fluid.
The continued development of capacity modulated scroll compressors has been directed towards the simplification of the capacity modulation devices in order to lower the costs of the capacity modulated systems, as well as simplifying the overall manufacture, design and development of these capacity modulated systems.
The present invention provides the art with a capacity modulated compressor which vents an existing intermediate pressurized chamber cyclically to suction to modulate the capacity of the compressor. The existing intermediate pressurized chamber is utilized in the compressor to bias the two scrolls together as well as to bias a floating seal into contact with a partition or the shell to seal a leakage passage between discharge pressure and the suction pressure zone of the compressor.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.